1. Field of the Invention
The present invention relates to a process for the production of polymers with hydroxyl groups. More specifically, the present process relates to a process for the production of polymers with hydroxyl groups by contacting a polymer having a substituent with high temperature, high pressure water, thereby introducing hydroxyl groups into the polymer.
2. Description of the Background
Polymers with hydroxyl groups are becoming increasingly useful because of their excellent properties, particularly including hydrophilicity and reactivity, and they have been the focus of much research in the past. An example is a process by which the surface of polyethylene is treated with a plasma, the result of which is the introduction of hydroxyl groups into the polymer (R. B. Blyth et al., Polym. Vol. 19 (1978), p. 1273). This process is based on plasma treatment, but the low reaction efficiency for hydroxyl group introduction has prevented its application beyond the experimental level.
Another example of a process of introducing hydroxyl groups into a polymer is the saponification of a carboxylic acid vinyl ester such as polyvinyl acetate to produce polyvinyl alcohol (PVA). Polyvinyl alcohol (PVA) is an industrially useful polymer employed for a variety of uses including the manufacture of fibers, paper, adhesives, emulsifiers and films. Polyvinyl alcohol is usually obtained by the saponification of polyvinyl acetate in an alcohol solvent such as methanol, using an alkali catalyst such as sodium hydroxide (Nagano et al., xe2x80x9cPovalxe2x80x9d (1970 edition), Kobunshi Publications). The saponification reaction is conducted by converting the acetoxyl groups of polyvinyl acetate to hydroxyl groups and it has been used industrially, but with the vast increase in the use of PVA in recent years there has been a desire to reduce the volatile organic components such as alcohol and the ash derived from the catalyst, that remain in the PVA.
When the conventional process is employed to conduct the above-described saponification reaction, it is difficult to completely remove impurities from the product, and this has led to suggestions that the process itself is in need of fundamental examination. Japanese Laid-open Patent Publication No. Hei-10-265507 proposes a process in which hydroxyl groups are introduced into a polymer having an electron attracting group by contact of the polymer with an alcohol at high temperature and high pressure. This process takes advantage of the solubilizing power of alcohols for polymers at high temperature and high pressure, and their ability to permeate into polymer particles and to allow introduction of hydroxyl groups into the polymer within a short period of time. The process is a very revolutionary process from the standpoint of reaction efficiency. Nevertheless, while this process permits the introduction of hydroxyl groups into the polymer within a short period of time, the above-mentioned problems of organic volatile components and ash remain unsolved.
Accordingly, one object of the present invention is to provide a process of producing polymers with hydroxyl groups in which the hydroxyl groups are introduced into the polymers in a short period of time and which results in a polymer product having a very low organic volatile component and ash content.
Briefly, this object and other objects of the present invention as hereinafter will become more readily apparent can be attained by a process of producing a polymer having hydroxyl groups, comprising:
contacting the polymer having a substituent with high temperature, high pressure water, thereby converting the substituent to hydroxyl groups.